Geology of the Semenyih Granite

132 Geology of the Semenyih Granite

MUHAMMAD BARZANI GASIM\ WAN NORAzMIN SULAIMAN2, MOHD. ISMAIL YAZIZ2, ABD. RAHIM SAMSUDIN1 AND WAN ZUHAIRI WANYAACOB1 1School of Environmental and Natural Resource Sciences Faculty Science and Technology, Universiti Kebangsaan Malaysia 43600 Bangi, Selangor 2Department of Environmental Science Faculty Science and Environmental Study Univerisiti Putra Malaysia

The Semenyih Granite is located in Mukim Semenyih, Hulu Langat. It was tectonically emplaced during the Late Mesozoic period. This granite intrudes Jelebu Schist in the northeast and Kajang Formation in the southwest. The mineral composition of the Semenyih Granite consists of 60-70% potash feldspar; 15-20% quartz; 5-15% plagioclase (oligoclase); 5-10% mica and 5% accessory minerals. The Semenyih Granite is divided into the Semenyih and Beroga Granites. Beroga Granite has medium to coarse grain texture and dark grey in color while Semenyih Granite has fme to medium grain texture and pale grey to light brown in color. The second texture formation due to tectonic events such as rotation of the crystal lattice, slip and rearrangement at grain boundaries, micro fractures and faults and fluid-filled micro fracture was observed under microstructure study. The microscopic evidence of deformation is compared with the macroscopic phenomenon of the Semenyih Granite. The northeastern area rock is characterized by cataclasites, strike -slip faults and highly fracture zones. It may be due to deformation after cooling or due to latest emplacement of this granite body, but the impact was lesser in the southwestern area. Field observations that the Semenyih Granite is highly weathered and severely eroded with landslides and rock falls occurrence locally, especially from Semenyih town to Sg. Lui road.

Warta Geologi, Vol" 27, No.3, May-fun 2001